The network operators may differentiate themselves by providing value-added services to the subscribers. One possibility for this is using the Intelligent Network (IN) architecture, or more recently, the IMS (IP Multimedia Subsystem) architecture. Providing privacy protection for the subscribers is one of the services customers demand. The basic privacy protection today is that the operators may offer private-number plans i.e. with numbers remaining unpublished in directories. The subscribers may also choose to disable their phone number (caller ID) when initiating a call.
A more evolved service available today is that the subscribers get a ‘virtual number’ that may be used to receive a call from an untrusted party. The subscribers may then tailor the usage of this virtual number in many ways e.g., by limiting the validity period. An example patent specification describing such a service is found in U.S. Pat. No. 5,590,184.
A common feature of the privacy services available today is that there is a trade-off between privacy and reachability of the subscriber. If one disables its phone number then others cannot reach him even when this would be desirable. Also, many phone owners hate phone calls from a secret number and they may choose not to answer the call if caller number is not visible. On the other hand, a virtual number provides only limited privacy in the sense that once the relation to the party that is using it is disclosed, anyone may abuse of it.
The virtual number services are also somewhat cumbersome to use since one has to register, and then manipulate the virtual numbers that are given. If used through a 3rd party provider, first a call should be made towards the virtual number and then another call should follow that will use in turn the virtual number as the calling party number. Yet another problem is that, when abuse is detected, the solution is to use call barring for the given virtual number, but this then applies to all involved parties, not only the abusing one. The impact may be partially diminished by using multiple virtual numbers, but this represents increased management overhead, and will also have cost impact as the pool of virtual phone numbers to use is limited and must be shared among all participants.
Thus there is a particular need for providing an enhanced privacy protection method, where the privacy and flexibility problems represented by using a generic virtual number are resolved, without increasing the management complexity either from operator or from customer side.